This invention relates generally to a signal control system, and more particularly to a system of this kind which is adapted to transmit to and receive from a remote location collective or distributed signals by the use of ring counter circuits.
Many of central administrative systems for monitoring and controlling a variety of signals employ a so-called two-line multiplex transmission system which permits transmission and reception of many signals with less conductive lines for the purpose of reducing wiring material. There have been proposed and practically used many systems employing a variety of circuit means in accordance with the purpose, use and conditions.
Such multiplex transmission system connects a pair of signal lines with multiple signal means which are respectively designated an address number. When signals are monitored or transmitted, an addressing function of all the transmitting means are always maintained in operating condition to confirm the address numbers. Also, the signal transmission is carefully checked, for example, by verification and double transmission, so as to avoid malfunctions caused by signal disturbance due to noise or the like. Thus, a great amount of pulses and transmission time are spent, for transmission and reception of only one signal, so as to improve the fidelity of signal.
Each signal means is supplied with an electric power from a pair of common lines for the indispensable addressing function. Therefore, even if integral circuits are employed to reduce the power consumption, a line current is increased in a monitoring condition as the number of connected signal means is larger.
In the above-mentioned multiplex transmission system, all the signal means are always operated simultaneously, and a current supplied to them is delivered through a pair of common lines, so that the current value becomes large in the whole system. A large line current implies a problem on a voltage drop, if supplied to signal means at remote locations, whereby several difficulties are encountered, for example, limitation of the number of connectable signal means, limitation in extendible distance of signal lines, requirement of large diameter wire, and so on.
Further, a double or even triple transmission of signal and verification are effected in order to ensure signal transmission and reception, whereby an amount of pulses used for each signal means is largely increased, with the result that the response time is delayed due to the redundancy of the transmission time. However, a high speed processing of pulses, for reducing the transmission time, can cause signal distortion and deteriorate noise durability. Also, in such case, a shield wire is employed for signal lines to ensure the stability. As a result, the production cost of the whole system is inevitably increased.
The unit of signal employed by the signal means is 2, 4, 8 and 16 units of the logical circuit. Also, in a facility where signals are distributed, wiring is arranged in a radial form directly from the signal means to a signal source. Therefore, several disadvantages will be present when a facility is to be enlarged or modified, for example, a portion of wiring becomes useless. Thus, the above-mentioned system is somewhat awkward to handle as a common line system.
Furthermore, integration of the signal means comprises following difficulties: First, the signal means uses many parts so that it is difficult to reduce its size. Employment of shield wire and the complicated arrangement makes the prime cost higher. Finally, since high technologies are applied to manufacturing, settlement and maintenance, larger expenses are required in every procedure.